White smoke reduction system for diesel vehicle

ABSTRACT

A white smoke reduction system for a diesel vehicle reduces white smoke generated from a diesel vehicle. The white smoke reduction system includes a diesel oxidation catalyst (DOC) mounted on an exhaust line connected to an engine to oxidize exhaust gas through a catalyst. A filter module is connected to a rear end of the DOC to collect particulate matter contained in the exhaust gas and is coated with a ceria (CeO 2 ) ingredient such that sulfur oxide is separated at a temperature equal to or more than 600° C.

CROSS-REFERENCE(S) TO RELATED APPLICATIONS

The present application claims the benefit of priority to Korean Patent Application Number 10-2014-0139782 filed in the Korean Intellectual Property Office on Oct. 16, 2014, the entire contents of which application are incorporated herein for all purposes by this reference.

TECHNICAL FIELD

The present disclosure relate to a white smoke reduction system, and particularly, to a white smoke reduction system capable of discharging sulfur oxide and water, which generate white smoke, at different temperature sections to suppress the sulfur oxide from reacting with the water.

BACKGROUND

Exhaust gas discharged from diesel engine vehicles significantly contains a variety of oxide and particulate matter, compared to gasoline engine vehicles. In recent years, efforts to reduce such noxious exhaust gas are ongoing.

FIG. 1 is a diagram illustrating a configuration of an exhaust line in a typical diesel vehicle. An engine 10, a diesel oxidation catalyst (DOC) 20, and a diesel particulate filter (DPF) 30 are sequentially provided at a set interval in the exhaust line of the typical diesel vehicle.

Particularly, in the diesel engine using fuel which contains 50 ppm or more of sulfur, sulfuric acid (H₂SO₄) in the form of steam is generated by the combination of sulfur oxide (SO₂) and H₂O in the process of removing particulate matter (PM) from the DPF 30. For this reason, the sulfuric acid (H₂SO₄) in the form of steam is cooled, and a particle size thereof is increased when the exhaust gas is discharged to the air, thus causing light scattering and white smoke.

A large quantity of white smoke is generated by evaporation of water contained in sulfuric acid (H₂SO₄) into steam when the sulfuric acid containing water is exposed at high temperature (for instance, approximately 400° C. to 600° C. during regeneration of the DPF) while being collected in a catalyst, an exhaust pipe, a muffler, etc. during traveling of the vehicle. Thus, reduction of the white smoke is performed through engine control.

A variety of white smoke reduction methods are currently proposed during regeneration of the DPF. However, such methods are not relatively effective since reducing white smoke through control of an engine or exhaust gas after-treatment device under a certain temperature.

Accordingly, a technique for controlling a temperature variation rate when the temperature of the exhaust gas after-treatment device increases according to a vehicle speed has been recently proposed.

However, since the conventional white smoke technique and the white smoke technique disclosed are performed through control of the engine or exhaust gas after-treatment device, the techniques require significant accuracy in controlling the engine or exhaust gas after-treatment device.

The matters described as the related art have been provided only for assisting the understanding for the background of the present disclosure and should not be considered as corresponding to the related art already known to those skilled in the art.

SUMMARY

An aspect of the present inventive concept is directed to a white smoke reduction system for a diesel vehicle, capable of discharging sulfur oxide (SO₂) and water (H₂O), which cause generation of white smoke by their reaction, at different temperature sections to suppress the sulfur oxide from reacting with the water.

Other objects and advantages of the present disclosure can be understood by the following description, and become apparent with reference to the embodiments of the present inventive concept. Also, it is obvious to those skilled in the art to which the present invention pertains that the objects and advantages of the present disclosure can be realized by the means as claimed and combinations thereof.

In accordance with an embodiment of the present inventive concept, a white smoke reduction system for a diesel vehicle, which reduces white smoke generated from a diesel vehicle, includes a diesel oxidation catalyst (DOC) mounted on an exhaust line which is connected to an engine to oxidize exhaust gas through a catalyst. A filter module is connected to a rear end of the DOC to collect particulate matter contained in the exhaust gas and is coated with a ceria (CeO₂) ingredient such that sulfur oxide is separated at a temperature equal to or more than 600° C.

The filer module may be a diesel particulate filter (DPF) connected to the rear end of the DOC. The DPF may be coated with the ceria ingredient.

The filer module may include a DPF connected to the rear end of the DOC and a white smoke reduction catalyst connected to a rear end of the DPF. The white smoke reduction catalyst may have a carrier through which the exhaust gas passes, and which is coated with the ceria ingredient.

A coating amount of the ceria ingredient may be 10% or more of an amount of a coating material coated on the DOC. The DPF includes a plurality of porous partition walls and collects the particulate matter passing through the DOC.

Platinum (Pt) may be contained in the coating material coated on the DOC.

The coating material coated on the DOC may include alumina (Al₂O₃) and zeolite. The coating amount of the ceria ingredient may be 50% or more of the amount of the coating material coated on the DOC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a configuration of an exhaust line in a typical diesel vehicle.

FIG. 2 is a diagram illustrating a configuration of a white smoke reduction system for a diesel vehicle according an embodiment of the present inventive concept.

FIG. 3 is a diagram illustrating a configuration of a white smoke reduction system for a diesel vehicle according another embodiment of the present inventive concept.

FIG. 4 is a graph indicating an increased temperature of a DPF, an SO₂ concentration, and white smoke generation according to post-injection in a comparative example.

FIG. 5 is a graph indicating an increased temperature of a DPF, an SO₂ concentration, and white smoke generation according to post-injection in an embodiment example.

DETAILED DESCRIPTION

Exemplary embodiments of the present inventive concept will be described below in more detail with reference to the accompanying drawings. The present inventive concept may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. Throughout the disclosure, like reference numerals refer to like parts throughout the various figures and embodiments of the present inventive concept.

FIG. 2 is a diagram illustrating a configuration of a white smoke reduction system for a diesel vehicle according an embodiment of the present inventive concept. FIG. 3 is a diagram illustrating a configuration of a white smoke reduction system for a diesel vehicle according another embodiment of the present inventive concept.

As shown in the drawings, the white smoke reduction system for a diesel vehicle according the embodiments of the present inventive concept includes a diesel oxidation catalyst (DOC) 20 which is mounted on an exhaust line connected to an engine 10 to oxidize exhaust gas through a catalyst. A filter module 100 or 200 is connected to a rear end of the DOC 20 to collect particulate matter contained in the exhaust gas and is coated with a ceria (CeO₂) ingredient such that sulfur oxide (SO₂) is separated at a temperature equal to or more than 600° C.

The engine 10 generates a driving force according to starting of a diesel vehicle, and serves to forcibly increase an exhaust temperature by performing post-injection according to control signals applied from an engine control unit (ECU) during regeneration of soot.

Here, the post-injection is to additionally inject fuel into high-temperature exhaust gas immediately after explosion in the intake, compression, and explosion/exhaust strokes of the engine 10 to increase the temperature of the exhaust gas according to additional combustion. The post-injection is performed under regeneration condition determination according to an accumulated amount of particulate matter (PM).

The DOC 20 reduces CO, HC, and the particulate matter in the exhaust gas discharged by driving of the engine 10, and converts NO into NO₂. Particularly, the DOC 20 also functions to adsorb a sulfur ingredient onto a coating layer in the form of SO₂.

In this case, the DOC 20 comprises a carrier made of a ceramic or metal material, and a surface of the carrier is coated with one or more of alumina (Al₂O₃), zeolite, and platinum (Pt) made of a catalytic material.

The filter module 100 or 200 improves a conventional diesel particulate filer (DPF). The filter module 100 or 200 physically collects the particulate matter in the exhaust gas, and combusts and reduces the particulate matter when the post-injection is performed. Particularly, the filter module 100 or 200 separates the SO₂ at a temperature equal to or more than 600° C. using the ceria ingredient in the present disclosure.

A diesel particulate filter (hereinafter, referred to as “DPF”) includes a plurality of porous partition walls and collects the particulate matter passing through the DOC 20.

As shown in FIG. 2, the filter module 100 according to an exemplary embodiment includes a DPF 110 which is arranged at the rear end of the DOC 20 and coated with the ceria ingredient.

In this case, an amount of the ceria ingredient coated on the DPF 110 may be 10% or more of an amount of a coating material coated on the DOC 20 when Pt is contained in the coating material coated on the DOC 20.

If the amount of the ceria ingredient is less than 10% of an amount of the coating material coated on the DOC 20, a separation temperature of the SO₂ may not be maintained at 600° or more due to a poor influence of the ceria ingredient.

However, when Pt is not contained in the coating material coated on the DOC 20 and the coating material mainly contains alumina (Al₂O₃) and zeolite, an amount of the ceria ingredient coated on the DPF 110 may be 50% or more of the amount of the coating material coated on the DOC 20.

As shown in FIG. 3, the filter module 200 according to another embodiment includes a conventional DPF 210 arranged at the rear end of the DOC 20 and a carrier 220 which is arranged at a rear end of the DPF 210 and coated with the ceria ingredient.

In this case, the carrier 220 may be realized in a filter form having various shapes such that the exhaust gas may pass through the carrier 220.

An amount of the ceria ingredient coated on the carrier 220 may be 10% or more of the amount of the coating material coated on the DOC 20 when Pt is contained in the coating material coated on the DOC 20, similar to the amount of the ceria ingredient coated on the DPF 110. In addition, when Pt is not contained in the coating material coated on the DOC 20, and the coating material mainly contains Al₂O₃ and zeolite, an amount of the ceria ingredient coated on the carrier 220 may be 50% or more of the amount of the coating material coated on the DOC 20.

Performance of the white smoke reduction system for a diesel vehicle as described above according to the present disclosure will be described according to comparison of a comparative example and an embodiment example.

First, a white smoke generator in the diesel vehicle is simply described.

The fuel used in the diesel engine 10 contains a predetermined sulfur ingredient, and sulfur oxide (SO₂) is generated in the combustion process. The sulfur oxide is present in exhaust gas in a state of absorbing water.

The sulfur oxide is adsorbed onto the DOC 20 and the DPF 30 at a low temperature equal to or less than 400° C. during discharge of the exhaust gas, and is collected. Subsequently, when the temperatures of the DOC 20 and the DPF 30 are increased by the post-injection, the adsorbed sulfur oxide is separated and sulfuric acid (H₂SO₄) in the form of gas is generated by reaction of the separated SO₂ and pyrolyzed H₂O due to high temperature. A temperature of the generated sulfuric acid is decreased while the sulfuric acid is discharged to the air together with the exhaust gas, and thus, the sulfuric acid is discharged in the form of white smoke.

Next, an SO₂ concentration and white smoke generation in exhaust gas are compared according to the comparative example and the embodiment example.

In the comparative example, the post-injection is performed on the exhaust line configured of the conventional DOC 20 and DPF 30. In the embodiment example, the post-injection is performed on the exhaust line having the DOC 20 and the ceria-coated DPF 110 according to the embodiment of the present inventive concept. The results according to these examples are shown in FIGS. 4 and 5.

FIG. 4 is a graph indicating an increased temperature of the DPF, the SO₂ concentration, and the white smoke generation according to the post-injection in the comparative example. FIG. 5 is a graph indicating an increased temperature of the DPF, the SO₂ concentration, and the white smoke generation according to the post-injection in the embodiment example.

As seen in the comparative example of FIG. 4, it is identified that opacity is increased to 50% while a large quantity of sulfur oxide (SO₂) is discharged in a case in which a temperature T5 measured at a front end of the DPF 30 when the temperature of the DPF 30 increases by the post-injection is between 400° C. and 600° C., and thus, a large quantity of white smoke is discharged.

In other words, the sulfur oxide collected at a low temperature (a temperature equal to or less than 400° C.) when the DPF 30 is forcibly regenerated is separated in quantity between a temperature of 400° C. and 600° C., and sulfuric acid (H₂SO₄) is excessively generated by reaction of the sulfur oxide (SO₂) with H₂O, which is present as a compound in the exhaust line, as the temperature of the H₂O increases. Consequently, a large quantity of white smoke is discharged.

On the other hand, as seen in the embodiment example of FIG. 5, it is identified that a large quantity of sulfur oxide (SO₂) is discharged in a case in which the temperature T5 measured at a front end of the DPF 110 when the temperature of the DPF 110 increases by the post-injection is equal to or more than 600° C. (620° C. to 650° C.), but opacity is maintained to the level of 10% or less, and thus, discharge of white smoke is suppressed.

This is because the sulfur oxide collected at a low temperature (a temperature equal to or less than 400° C.) when the DPF 110 is forcibly regenerated is separated in quantity at a temperature equal to or more than 600° C., but H₂O, which is collected as a compound in the exhaust line, is discharged and exhausted, and thus, H₂O gas amount decreases rapidly at a temperature section equal to or more than 600° C. Thus, since an amount of H₂O to be reacted remarkable decreases even though the sulfur oxide (SO₂) separated at the temperature section equal to or more than 600° C. is discharged, the reaction of the sulfur oxide (SO₂) and the H₂O is suppressed so that the white smoke is nearly invisible with the naked eye.

Accordingly, according to the comparison of the above-mentioned comparative example and embodiment example, when the ceria-coated DPF 100 is applied, the sulfur oxide is separated at a temperature equal to or more than 600° C. instead of the conventional temperature of 400° C. to 600° C., and the H₂O is discharged. Thus, since the sulfur oxide is separated in a state in which the H₂O is beforehand exhausted at a temperature less than the separation temperature of the sulfur oxide, the sulfur oxide is suppressed from reacting with the H₂O. Therefore, it may be possible to suppress the generation of the white smoke while the sulfuric acid (H₂SO₄) generated by the reaction of the sulfur oxide (SO₂) and the H₂O is discharged to the air.

An experimental result in which the post-injection is performed on the exhaust line having the DOC 20, the DPF 210, and the ceria-coated carrier 220 according to another embodiment also shows a pattern which is nearly similar to the above-mentioned experimental result in FIG. 5.

In accordance with the exemplary embodiments of the present inventive concept, sulfur oxide and water may be discharged at different points of time by coating a ceria ingredient on a diesel particulate filter (DPF) or on a carrier which is separately installed at a rear end of the DPF such that sulfur oxide is separated at a higher temperature than a temperature section at which the water is discharged.

Thus, it may be possible to prevent generation of white smoke by suppressing the sulfur oxide from reacting with the water.

While the present disclosure has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. 

What is claimed is:
 1. A white smoke reduction system for a diesel vehicle, which reduces white smoke generated from a diesel vehicle, the system comprising: a diesel oxidation catalyst (DOC) mounted on an exhaust line connected to an engine to oxidize exhaust gas through a catalyst; and a filter module connected to a rear end of the DOC to collect particulate matter contained in the exhaust gas, the filter module being coated with a ceria (CeO₂) ingredient such that sulfur oxide is separated at a temperature equal to or more than 600° C.
 2. The white smoke reduction system of claim 1, wherein: the filer module is a diesel particulate filter (DPF) connected to the rear end of the DOC; and the DPF is coated with the ceria ingredient.
 3. The white smoke reduction system of claim 1, wherein: the filer module comprises a DPF connected to the rear end of the DOC and a white smoke reduction catalyst connected to a rear end of the DPF; and the white smoke reduction catalyst includes a carrier through which the exhaust gas passes, the carrier being coated with the ceria ingredient.
 4. The white smoke reduction system of claim 2, wherein a coating amount of the ceria ingredient is 10% or more of an amount of a coating material coated on the DOC.
 5. The white smoke reduction system of claim 4, wherein platinum (Pt) is contained in the coating material coated on the DOC.
 6. The white smoke reduction system of claim 4, wherein the coating material coated on the DOC comprises alumina (Al₂O₃) and zeolite, and a coating amount of the ceria ingredient is 50% or more of the amount of the coating material coated on the DOC.
 7. The white smoke reduction system of claim 3, wherein a coating amount of the ceria ingredient is 10% or more of an amount of a coating material coated on the DOC.
 8. The white smoke reduction system of claim 2, wherein the DPF includes a plurality of porous partition walls and collects the particulate matter passing through the DOC. 